Sudoku.gms : Solve a Sudoku in Excel, using the GDX DLL (vba API) and the GAMS executable

Description

In this example GAMS runs only in the background. We use the vba version of the
GDX API to write a GDX file from data defined in the spreadsheet. To solve the
model we call the GAMS executable with a CreateProcess call out of vba.

$Title Sudoku in Excel
$Ontext
In this example GAMS runs only in the background. We use the vba version of the
GDX API to write a GDX file from data defined in the spreadsheet. To solve the
model we call the GAMS executable with a CreateProcess call out of vba.
$Offtext
$if %system.filesys% == UNIX $abort.noerror 'This model cannot run on a non-Windows platform';
$call msappavail -Excel
$if errorlevel 1 $abort.noerror 'Microsoft Excel is not available!';
$call "start sudoku.xls"